It is well known to line wellbores with liners or casing and the like and, thereafter, to create flowpaths through the casing to permit fluids, such as fracturing fluids, to reach the formation therebeyond.
One such conventional method for creating flowpaths is to perforate the casing using apparatus such as a perforating gun, which typically utilize an explosive charge to create localized openings through the casing.
Alternatively, the casing can include pre-machined ports, located at intervals therealong. The ports are typically sealed during insertion of the casing into the wellbore, such as by a dissolvable plug, a burst port assembly, a sleeve or the like. Optionally, the casing can thereafter be cemented into the wellbore, the cement being placed in an annulus between the wellbore and the casing. Thereafter, the ports are typically selectively opened by removing the sealing means to permit fluids, such as fracturing fluids, to reach the formation.
Typically, when sleeves are used to seal the ports, the sleeves are releasably retained thereover and can be actuated to slide within the casing to open and close the respective ports. Many different types of sleeves and apparatus to actuate the sleeves are known in the industry. Fluids are directed into the formation through the open ports. At least one sealing means, such as a packer, is employed to isolate the balance of the wellbore below the sleeve from the treatment fluids.
A variety of tools are known for actuating sleeves in ported subs including the use of shifting tools, profiled tools and packers. In U.S. Pat. No. 6,024,173 to Patel and assigned to Schlumberger, a shifting tool and a position locator is disclosed for locating a downhole device and engaging a packer element within moveable member and operating the device using and applied axial force to shift the member.
In Canadian Patents 2,738,907 and 2,693,676, both to NCS Oilfield Services Canada Inc., a bottom hole assembly (BHA) is deployed at an end of coiled tubing and located adjacent a ported sub by a sleeve locator. The BHA has a sealing member and an anchor such as a releasable bridge plug or well packer, which are set inside the ported sub fit for shifting a sliding sleeve and opening ports to the wellbore. From an uphole end, the BHA is connected to coiled tubing, has a fluid cutting assembly (jet cutting tool), a check valve for actuating the jet cutting tool, a bypass/equalization valve and the sealing member, the releasable anchor and the sleeve locator. A multifunction valve, including reverse circulation and pressure equalization, is positioned between the abrasive fluid jetting assembly and the sealing element. Set down on the coiled tubing closes the multifunction valve, blocking fluid communication to the tubing below the sealing member, and aligning ports in the valve for reverse circulation between the annulus and one way flow up the coiled tubing through the check valve. Pull up on the coiled tubing opens the multifunction valve to permit flow through a port in the valve between the annulus and the tubing the below the sealing member for equalization and though the port in the valve between the annulus and one way flow up the coiled tubing for reverse circulation. The check valve prevents fluid delivered through the coiled tubing from moving beyond the jetting assembly. Thus, fluid delivered through the coiled tubing is only used to cut perforations. Treatment fluid, such as for fracturing, is delivered through the annulus, between the BHA and the casing, to the ports opened by the sleeve.
As one of skill will appreciate, the volume of treatment fluid which must be pumped through the annulus is significantly larger than that which would be required to be pumped through the coiled tubing to achieve relatively the same result. Not all formations require such volumes and the cost of treatment fluids is not inconsequential to the overall costs of a fracturing operation.
There is interest in the industry for robust apparatus and methods of performing completion operations which are relatively simple, reliable and which reduce the overall costs involved.